Prescription eyeglass lenses have conventionally been produced by providing a pair of lens blanks, of glass or plastic, having two major lens surfaces. One of these surfaces is cut with a grinding tool to generate a lens surface having a shape closely approximating that of the prescribed lens. The ground lens surface is then fined by rubbing this surface with a lap having an abrasive surface to create a surface form that meets the prescription, and the fined surface is then polished to optical clarity. If desired, the lens may then be coated for tinting, antireflection, scratch resistance, etc.
One of the drawbacks of this conventional approach is that it is relatively time consuming and requires a significant amount of expertise and expense. Although computer-controlled machinery has been developed and is now widely used to quickly generate, fine and polish lens blanks to meet any prescription, this equipment is relatively expensive, preventing its use by most optometrists and/or merchants. Accordingly, rather than stock eyeglass lenses for all potential customers' prescriptions, these individuals and/or companies have been required to order lenses for many prescriptions from a distant laboratory or manufacturer, requiring their customers to wait one or more days to receive their eyeglasses.
In an attempt to avoid these and other drawbacks associated with conventional eyeglass lens production, several manufacturers have been working to develop wafer lamination systems wherein a front lens wafer and a back lens wafer are laminated together to form a composite lens. Each wafer is provided in finished and polished form so as to provide selected optical properties. In order to produce a particular prescription lens, selected front and back wafers are combined and aligned relative to each other so that the combined optical properties of the wafers form the prescribed lens. The primary advantage of this type of system is that a relatively small inventory of wafers may be stocked and used to make composite lenses satisfying hundreds of thousands of multi-focal and single-vision prescriptions. In addition, the wafers may be pre-tinted, or pre-coated with, for example, an anti-reflection or scratch-resistant coating, thus avoiding the need to send the lenses to a distant laboratory or like facility to apply such a coating as is now frequently required.
In a typical wafer lamination system, a composite lens is formed by placing the selected front lens wafer into a lens holder with its concave or back side facing up. A predetermined quantity of adhesive is then applied to the back side of the front wafer, and the convex or front side of a selected back lens wafer is then superimposed over the front wafer and aligned relative to the front wafer in accordance with the requirements of a particular prescription. The two lens wafers are then squeezed together to spread the adhesive throughout the interface between the wafers.
In conventional wafer lamination systems, mechanical clamping or pressing devices have been employed to press the lens wafers together. In other such systems, pneumatic pressure has been applied by superimposing an inflatable bladder over the lens assembly and inflating the bladder so that it engages and presses the lenses together against a compliant support surface. These types of prior art devices require relatively precise shape, construction, and positioning to provide uniform application of pressure and avoid distortion of the wafer pair.
Most current wafer lamination systems use an adhesive which is cured by exposure to ultraviolet (UV) light for bonding the lens wafers, and this is typically done during the step of pressing the wafers together. Accordingly, the mechanical pressing devices typically require an optically-transparent window, and the inflatable bladders have likewise been made of transparent materials to permit the transmission of UV light into the lens assembly when pressing the lenses together. One of the drawbacks of these current wafer lamination systems is that the inflatable bladder structures and transparent window assemblies may absorb a substantial portion of the UV light, thereby increasing the time required to cure the adhesive. In addition, the adhesive typically has oxygen-inhibited activators and thus any adhesive that spreads onto the edge surface areas of the wafer lamination remains in a wet or waxy state after curing. The wet adhesive may in turn be transferred by contact to the surfaces of the pressing devices, or to other components of the lamination system, requiring time-consuming clean up between lamination procedures. In addition, many current wafer lamination systems require extensive operator handling of the wafers, which likewise leads to contamination and/or damage to the wafers, particularly when operators are required to handle wafers having uncured adhesive on their edge surface areas.
Accordingly, it is an object of the present invention to overcome many of the drawbacks and disadvantages of such prior art wafer lamination systems.